A single field experiment was established in 2001 at the Safford Agricultural Center to evaluate the effects planting method and seeding rate have on plant population and yield of an Upland cotton cultivar Deltapine DP655BR. Two planting methods; planting into moisture (pre-irrigate) and dry plant/water-up, were main effects with three seeding rates of 10, 20, and 30 lbs./acre as sub-effects. These effects were evaluated with respect to stand establishment and yield. Analysis of variance showed no significant differences with respect to planting method for either plant population or yield, so data was combined across main effects. Significant differences were observed in plant population and yield as a function of seeding rate. A linear increase in yield with plant population was observed. These results are not consistent with previous research performed examining plant population effects on yield. This experiment will be conducted again in 2002 in an effort to validate results observed in 2001.

Field experiments were initiated in 2001 for a cotton-based conservation tillage project at sites in Marana, Coolidge, and Goodyear, Arizona. For the 2002 season, soil and water management assessments were made to evaluate surface irrigation performance under conservation tillage, following cover and grain crops. An additional site was added in the winter of 2002 at Maricopa, Arizona. Analyses included soil texture, infiltration rate, and water advancement. At Coolidge, conservation tillage plots had higher infiltration rates and longer advance times than the conventional plots in 2002 and 2003. At Marana, infiltration rates were initially higher for the Conservation plots but the rates converged at the end of four hours in 2002. In 2003, Conventional plots infiltrated about one inch more. Advance times for Marana showed water infiltration for Conventional wheel rows to be the fastest. At Goodyear, Conservation plots infiltrated more than Conventional plots during 2002. This also resulted in a slower advance time for the Conservation plots. In 2003, treatment effects were not comparable due to tillage by the grower. At Maricopa, Conservation plots infiltrated almost 2.2 inches more water than Conventional plots and water reached the end of the field three hours ahead of the fastest Conservation plot. Seasonal irrigation water applications to each treatment were relatively equal for all sites with the exception of Coolidge. Here, the long field combined with sandy soil made it difficult to adequately irrigate the Conservation plots. In 2002, an additional 21 inches of water was applied to the Conservation plots. In 2003, that amount was reduced to 12.5 inches. The yield data show a significant difference in 2002 only at Coolidge. There, Conservation plots yielded more than the Conventional ones. This may have been due to more water applied to the Conservation plots. In 2003, the opposite occurred with the Conventional plots yielding more than the Conservation plots. This could have been due to herbicide damage. At Maricopa, the Conventional plot also yielded more than the Conservation plot. Initial indications are that the conservation tillage does impact irrigation performance and may not be suitable for all locations depending on soil type and field layout.

Foliar fertilizers are not widely used for cotton production in the low desert, and data about their effects on cotton production under these conditions is therefore limited. This study documented the effects of Calcium Metalosate7 and Megafol, each applied at the rate of 1 qt/acre to DPL555BR cotton. Treatments were applied on July 7, and plants had been growing vigorously just prior to application. Plots were approximately 0.75 acres in size with four replications. Plant mapping data from late July indicated that non-treated cotton had numerically higher retention rates at each of the first three fruiting positions mapped in addition to slightly more total nodes and a greater number of reproductive nodes in part due to first fruiting structure being retained lower on the plant (node 6.75) than treated cotton (node 7.95 for Megafol, node 8.4 for Calcium Metalosate7). Tractor passage through treated plots may have also knocked off developing squares however. No statistical differences were noted for lbs. of lint/acre, although treated cotton did have slightly higher yields than the untreated check (1,162 lbs/acre) and treatments were almost identical (1,203 lbs./acre for Megafol; 1,198 lbs./acre for Calcium Metalosate7). Fiber lengths and strengths were significantly different by treatment, with shortest and weakest fibers resulting from cotton treated with Megafol. Cotton from Calcium Metalosate7 treatments were significantly longer and stronger than lint from Megafol treated cotton plots, but lint from untreated cotton plots was significantly longer and stronger than either treatment (36.6 staple, 31.0 g/tex). The reasons for these differences are unclear. It is difficult to correlate the slight yield increases noted with treatments in early July, especially in light of lower retention rates noted with treatments from plant mapping data in late July and the large amount of lint production that occurred in late 2003 due to summer heat. Multiple differences were noted for treatments in regards to lint quality, however, indicating treatments did affect cotton production. Size of bolls and cotton lint from these early summer bolls was not obtained but may have been an overlooked aspect of this study.

A single field study was established to evaluate the effects of planting date (PD) on the yield and fiber quality characteristics of several cotton varieties commonly grown in the Upper Gila River Valley of Safford. Eight varieties selected for evaluation in 2003 ranged from medium to medium-full varieties. These varieties included two Delta and Pine varieties (DP555BR and DP655BR), two Fiber Max varieties (FM989BR and FM991BR), two Stoneville varieties (ST5303R and ST5599BR), one CPCSD variety (Riata), and one variety from the Arizona Cotton Growers Association breeding program (AG3601). These eight varieties were planted on three separate planting dates (1 April, 23 April, and 12 May; 341, 525, and 779 heat units accumulated after January 1, respectively) in a split-plot within a randomized complete block design with four replications. Overall analysis of variance revealed significant differences due to main effects (PD; OSL=0.00043), sub effects (variety; OSL=0.0029), and interaction effects (PD*variety; OSL=0.0266). Extremely cool conditions surrounding the first PD resulted in significantly lower yields that the other two planting dates. Yields for PD 1 ranged from 506 lbs. lint/acre to about 850 lbs. lint/acre with DP555BR producing the highest and CPCSD Riata producing the lowest yield. Conditions surrounding the second PD were much improved over PD 1. However, soil temperatures still hovered near to and below the optimum temperature of 65oF. Yields were dramatically higher in PD 2 when compared to PD 1, ranging from a low of 847 lbs. lint/acre (AG3601) to 1139 lbs. lint/acre (FM991BR). PD 3 resulted in the best conditions for seedling emergence and stand establishment and produced the highest yield. Yields ranged from a low of 945 lbs. lint/acre (CPCSD Riata) to 1465 lbs. lint/acre (FM991BR). Fiber quality data demonstrated a couple of interesting trends. Micronaire tended to increase with later plantings for most varieties while fiber length had an inverse relationship with PD. Micronaire levels tended to be high enough to be discounted for every variety in at least one and usually two PDs, except for Riata. Riata had the lowest micronaire, and the longest and strongest fiber grades. These results are consistent with other evaluations of the high fiber quality associated with many of the California Acala varieties. However, relatively lower yields for this variety currently make it an unsuitable variety for this region despite the high fiber quality. Results from this evaluation demonstrate the importance of monitoring soil temperature and keeping a close eye on local weather forecasts when making planting date decisions regardless of the calendar date.

Arizona cotton experienced a severe crisis in 1995 stemming from resistance of whiteflies to synergized pyrethroid insecticides. The insect growth regulators (IGRs) Knack® (pyriproxyfen) and Applaud® (buprofezin) served a pivotal role in resolving this problem. Statewide monitoring of whitefly resistance is conducted annually in Arizona to assess the status of resistance in this important pest. In this paper we provide an update on results from whitefly collections made from 19 cotton fields located throughout Arizona. Overall, whitefly control in Arizona cotton remained excellent in the 2001 season and there were no reported field failures. However, we detected major decreases in susceptibility to Knack of whiteflies collected from cotton. Whereas it was extremely rare to have any whiteflies surviving bioassays of 0.1 μg/ml from 1996 to 1998, this changed in 1999, and by the 2001 season over 60% of Arizona sites evaluated had •2% pyriproxyfen-resistant whiteflies. One collection from Eloy, Arizona, in 2000 had >50% of whiteflies surviving Knack bioassays of 0.1 μg/ml. Whiteflies throughout Arizona continued to be moderately less susceptible to Applaud, relative to susceptibility levels in 1996, when the IGRs were first introduced. In contrast to our findings with Knack, changes in susceptibility to Applaud have been only moderate and quantitative. Arizona whiteflies continued a six year trend of reduced resistance to synergized pyrethroid insecticides, as indicated by bioassays with mixtures of Danitol and Orthene. Problematic frequencies of whiteflies resistance to synergized pyrethroids were found at only two of 19 locations sampled. Steps should be taken now to prepare for the onset of more severe resistance to IGRs in Arizona cotton. Factors that could undermine the current success of whitefly resistance management in Arizona are discussed. Education efforts should reinforce the importance of limiting IGR use in cotton to a maximum of one treatment each per season and rotating conventional insecticides as recommended in the three-stage resistance management strategy implemented in 1996. Because Knack and Applaud have received registrations for use in Arizona vegetable and melon crops grown in proximity to cotton, it is now especially critical that Extension education efforts focus on cross-commodity coordination of IGR use recommendations to preserve the activity of these important insecticides.

A series of studies were conducted around the southeastern region of the state during the 2002 cotton growing season to evaluate the effects of a twin-line (TL) planting configuration on fiber quality and lint yield. Two of the three studies were conducted on grower cooperator fields with large block comparisons or demonstrations of TL versus single-line (SL) configurations. Fiber quality was essentially the same for both demonstration locations. Yield differences were observed in both locations with the Graham County location experiencing a 130 lb lint yield decrease in the TL plots. The Cochise County location experienced a 328 lb lint yield increase in the TL plots. The third study was a split plot within a randomized complete block design with planting configuration (TL or SL) as the main effect and variety as the sub-unit effect. . No significant differences were detected in the main effect, sub effect or the interaction with respect to yield. Trends were observed however, indicating less difference between the TL and SL with respect to yield for varieties with a more columnar growth pattern. Fiber quality results indicated no significant differences among any of the treatments

Twelve varieties were tested including two new herbicide resistant entries from California, Riata and Nova, two New Mexico Acalas, seven roundup resistant entries from Delta and Pine Land Co., Stoneville, SureGrow and FiberMax, and the new variety developed for the Arizona Cotton Grower’s Association, AG 3601. The highest yielding variety in the trial was FM 989 with a yield of 1045 pounds of lint per acre. It was also the highest yielding variety at this location last year. The Acala 1517-99 placed second in yield at 1039 pounds of lint per acre. HVI data are also included in this report.

Studies were conducted to follow seasonal susceptibility of feral pink bollworm (PBW), Pectinophora gossypiella (Saunders) larvae to NuCOTN 33B (Bt) and Deltapine (DPL) 5414 in furrow and furrow plus supplementary drip-irrigated cotton field plots. Laboratory bioassays of laboratory - reared PBW larvae to flower buds and bolls and cabbage looper (CL), Trichoplusia ni (Hübner), larval mortality feeding on DPL 5415 and Bt cottons leaves were also conducted. Cry1Ac insect toxic protein contents in the different plant tissue were determined by Enzyme Linked ImmunoSorbent Assay (ELISA) throughout the season to compare in relation to PBW and CL mortality data. Irrigation type had no effect on PBW or CL larval mortality parameters measured. DPL 5415 bolls had 0.15 feral live larvae per boll and no dead larvae per boll compared with no live and 0.12 dead feral larvae per Bt boll. Whole plant samples showed 0.5 to 8.6% live larvae boll infestations compared to no live PBW life stages and no exit holes for Bt bolls. No PBW larvae survived on day four following bioassay infestation of one-third grown Bt flower buds with PBW neonate larvae as compared to 90% larval survival on DPL 5415 flower buds. Immature bolls harvested in the field and artificially infested with PBW larvae in the laboratory showed averages of 3 to 52% live larvae per boll, all in fourth instar of development, for DPL 5415 bolls compared to no live larvae, no development beyond the first instar, and no exit holes for Bt bolls. Cry1Ac protein level in flower buds were 0.11 to 0.16 ppm and 0.14, 0.11 and 0.05 ppm, in each case, per wet weight gram of boll tissue in bolls during the season. For CL leaf bioassays, larval mortalities after 7 days feeding on Bt leaves were variable ranging from 82 to 94% from node 8 on 61 and 82 days after planting (DAP) to 32, 38 and 7% on leaves from node 16 on 82, 117, and 159 DAP, respectively, and 28 and 6% on leaves from node 24 on 117 and 159 DAP. Cry1Ac amounts were 0.96 and 0.85 ppm (wet wgt per g of Bt leaf tissue), from leaves from node 8 (61 and 82 DAP), 0.53, 0.50 and 0.22 ppm (node 16, 82, 117, and 159 DAP) and 0.44 and 0.18 ppm (node 24, 117 and 159 DAP). Numbers of cotton bolls, lint and seed per acre were significantly greater from plots that were furrow plus drip irrigated as compared to furrow irrigated alone. DPL 5415 and Bt cotton yields were not significantly different.

Genetically modified cotton expressing the Cry1Ac toxin has been used in Arizona since 1996 with exceptionally positive results in terms of economic returns to growers and reductions in insecticide use in cotton. Since 1995, average insecticide use in Arizona cotton has declined from greater than six applications per acre to less than two in 2000. Bt cotton has contributed greatly to these savings to growers, as have insect growth regulators used for whitefly control. Collections of pink bollworm, Pectinophora gossypiella, made in 1997 and subsequently exposed to Cry1Ac in the laboratory from 1998 to 2000, yielded a laboratory strain with susceptibility to Cry1Ac reduced 1,000 to 3,000- fold, relative to highly susceptible field populations. Unparalleled measures have been taken to detect and manage this resistance. In this report we summarize results of statewide monitoring of pink bollworm susceptibility to Cry1Ac conducted from 1997 to 2000, and results of field evaluations of the effectiveness of Bt cotton from 1995 to 2001. Susceptibility of Arizona pink bollworm to Cry1Ac, increased from 1997 to 2000. Mean corrected mortality in 1μg/ml Cry1Ac assays was 57.4% in 1997, 90.6% in 1998, 97.9% in 1999 and 97.4% in 2000. Mean corrected mortality in bioassays of 10 μg/ml also increased: it was 94.1% in 1997, 99.9% in 1998, 100% in 1999 and 100 % in 2000. Field performance of Bt cotton in 2000 continued to be excellent at 39 locations throughout Arizona cotton at which paired Bt and non-Bt fields were evaluated. Whereas non-Bt cotton fields had mean infestations of over 15% infested bolls, Bt cotton fields averaged less than 0.15% infested bolls. Thus, after six years of intensive use of Bt cotton in Arizona, pink bollworm populations show no signs of being resistant to Bollgard cotton. Indeed, for reasons that are not understood at this time, they have been found to be significantly more susceptible to the Bt toxin in Bollgard cotton at the end of the 2000 season than they were in 1997.

Pink bollworm (PBW), Pectinophora gossypiella (Saunders), diapause larval exit from immature green bolls and larval and pupal mortality after exiting bolls, were studied at Phoenix, AZ in the insectary. Diapause larvae exited immature bolls sporadically during January, February, and early March. Thereafter, exit from the bolls was more consistent and highest numbers emerged in late April, May or early June. Larval and pupal mortality were high during January to early February and March, decreased in mid-March through early June, and increased again in mid-June to early August. Larvae remained in immature bolls as long as 319 days after harvest. Moth emergence was significantly correlated to accumulated heat units (12.8 and 30.6°C lower and upper developmental thresholds).

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